Static and dynamic autonomic response with increasing nausea perception

Abstract

Background: Nausea is a commonly occurring symptom typified by epigastric discomfort with urge to vomit. The relationship between autonomic nervous system (ANS) outflow and increasing nausea perception is not fully understood.

Methods: Our study employed a nauseogenic visual stimulus (horizontally translating stripes) while 17 female subjects freely rated transitions in nausea level and autonomic outflow was measured (heart rate, HR; heart rate variability, HRV; skin conductance response, SCR; respiratory rate). We also adopted a recent approach to continuous high-frequency (HF) HRV estimation to evaluate dynamic cardiovagal modulation.

Results: HR increased from baseline for all increasing nausea transitions, especially transition to strong nausea (15.0 +/- 11.4 bpm), but decreased (-6.6 +/- 4.6 bpm) once the visual stimulus ceased. SCR also increased for all increasing nausea transitions, especially transition to strong nausea (1.76 +/- 1.68 microS), but continued to increase (0.52 +/- 0.65 microS) once visual stimulation ceased. LF/HF HRV increased following transition to moderate (1.54 +/- 2.11 a.u.) and strong (2.57 +/- 3.49 a.u.) nausea, suggesting a sympathetic shift in sympathovagal balance. However, dynamic HF HRV suggested that bursts of cardiovagal modulation precede transitions to higher nausea, perhaps influencing subjects to rate higher levels of nausea. No significant change in respiration rate was found.

Conclusions: Our results suggest that increasing nausea perception is associated with both increased sympathetic and decreased parasympathetic ANS modulation. These findings corroborate past ANS studies of nausea, applying perception-linked analyses and dynamic estimation of cardiovagal modulation in response to nausea.

Figure 1

Experimental procedure and analysis approach. (A) Subjects lay supine while a nauseogenic visual stimulation (horizontally translating stripes) was projected onto a full field-of-view screen from behind. (B) The visual stimulus was comprised by cross-hair fixation for 5 minutes before and after linear vection stimulus, which lasted up to 20minutes, or until the subjected rated a nausea level “4” for “severe” nausea. (C) Autonomic data were analyzed with both a stimulus-based (left) and percept-based (right) approach, where data averaged over discrete windows were compared to data collected during cross-hair fixation at baseline.

Figure 2

Stimulus-based analysis of physiological indices. (A) Timing of 4-minute windows of interest are shown over a plot of a representative subject's nausea level. (B–G) Average change in skin conductance, HR, respiratory rate, normalized HF, normalized LF, and LF/HF ratio demonstrated significant increase in SCR and HR, and a trending increase in LF/HF ratio in response to increasing duration of nausea stimulus. While SCR remained elevated after cessation of nauseogenic stimulus, HR significantly decreased. Error bars indicate standard error of the mean. (+ 0.1>p>0.05,*0.05> p>0.01, **0.01>p>0.001, ***p<0.001).

Figure 3

Percept-based analysis of physiological indices. (A) Timing of 4-minute baseline and 1-minute post nausea rating transition windows are shown over a plot of a representative subject's nausea level. (B–G) Mean change in SCL, HR, respiratory rate, normalized HF, normalized LF, and LF/HF ratio reveal increases in SCL, HR, normalized LF, and LF/HF ratio with increasing nausea level. HF normalized decreased in response to increasing nausea level. Error bars indicate standard error of the mean. (+ 0.1>p>0.05,*0.05> p>0.01, **0.01>p>0.001, ***p<0.001).

Figure 4

Average across subjects of normalized point process HF HRV. (A) Schematic representation of the 90-second window placements. (B–F) HF HRV timeseries within windows of interest averaged across subjects demonstrate robust gradual decrease following stimulus initiation and gradual increase following stimulus cessation. Phasic bursts of HF power are noted prior to change in nausea perception.